@suportemd said:
I work at the ISP, checked all the possibilities and can not find anything that might be blocking.

Most ISPs who block access to services, do so without informing their customer or giving customers a way to remove this block themselves. I’m not sure which possibilities you checked, I would just like to say that the absence of a block list or block/unblock button does not prove the absence of any blocking.

A good way to figure out if it’s something on our end or on your end is by doing a “traceroute”. You can find many guides online on how to do this from your computer (Windows, Mac, Linux, something else). Can you please do a traceroute and paste the results here?

Yes, the final hop is from our network, so at least not all connections to the server are being blocked.

Still, that doesn’t automatically conclude that there are no blocks. It’s still possible that there is a firewall restricting FTP connections. Which could be on our end or yours. But to my knowledge, we don’t block any IP addresses for FTP.